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Large prospective cohort studies have consistently shown that physical inactivity and low levels of cardiorespiratory fitness are strong and independent predictors of all-cause and cardiovascular mortality in men and women. The risk of premature death is estimated to be 25% to 50% lower for those who are fit compared with those who are unfit.1 Among healthy children, higher levels of physical activity and cardiorespiratory fitness are independently associated with a favourable metabolic risk profile.2
Direct assessment of cardiorespiratory fitness is performed by measuring peak oxygen uptake (peak VO2, L/min) during a maximal exercise test. This requires simultaneous measurement of respiratory gas exchange by indirect calorimetry and is usually performed in a controlled environment. However, field tests that measure exercise capacity and heart-rate responses are available and are frequently used as surrogates.
Lammers et al3 present data on normal values for the 6-minute walk test in children aged 4 to 11 years of age. The 6-minute walk test was originally developed to assess exercise capacity in patients with pulmonary or cardiovascular disease.
CARDIORESPIRATORY FITNESS IN CHILDREN
The measurement of cardiorespiratory fitness and exercise capacity in children goes back some 70 years. In 1938, Sid Robinson published his classic paper, “Experimental studies on physical fitness in relation to age”,4 which was followed by the pioneering studies by Åstrand on physical work capacity in boys and girls.5
Thereafter, numerous cross-sectional and longitudinal studies have shown that peak VO2 in boys increases progressively with age. Data …